This application claims priority from the Swedish patent applications Nos. 9900445-9 and 9904256-6, which hereby are incorporated in their entireties and for all purposes by reference.
The present invention relates to an antenna device for transmitting and receiving RF waves in at least a first frequency band and comprising a support structure and at least one radiating antenna portion carried by the support structure.
The invention also relates to a radio communication device including such an antenna device.
In the radio communication systems of today there is an ever increasing demand for making the user devices smaller. This is especially important when it comes to handportable terminals, e.g. portable phones a design of the handportable terminals must permit the terminals to be easily and rapidly manufactured at low costs. Still the terminals must be reliable in use and exhibit a good performance.
It is well known that the size of an antenna is critical for its performance, see Johnsson, Antenna Engineering Handbook, McGrawHill 1993, chapter 6. The interaction between antenna, phone body and the close-by environment, such as e.g. the user himself, will become more important than ever.
This puts requirements on the antenna device to be compact, versatile and to have good antenna performance. It must also be robust, stable, easy to mount, easy to connect, and arranged so as to efficiently use the available space. Interest has also been focused on antenna devices mounted inside the housing of hand-portable terminals. Thereby, protruding antenna parts are avoided.
The radiating properties of an antenna device for a small-sized structure, e.g. for a handportable terminal, such as a portable phone, depends heavily on the shape and size of the support structure, e.g. a printed circuit board, PCB, of the phone, and also on the phone casing. All radiation properties, such as resonance frequency, input impedance, radiation pattern, impedance, polarization, gain, bandwith, and near-field pattern are products of the antenna device itself and its interaction with the PCB and the phone casing. On top of this, objects in the close-by environment affects the radiation properties. Thus, all references to radiation properties made below are intended to be for the whole device in which the antenna is incorporated.
What has been stated above is true also with respect to radio communication systems used in other apparatus than portable phones, such as cordless telephones, telemetry systems, wireless data terminals, etc. Thus, even if the antenna device of the invention is described in connection with portable phones it is applicable on a broad scale in various radio communication apparatus.
As the rate at which new models of portable phones are presented is increasing, the time from start of the development of a new model to the start of production and marketing of the same has been drastically shortened during the last few years. Further, there is a demand for a reduction of the manufacturing costs at the same time as the technical requirements are increasing which necessitates more functions to be included in each unit. Further, the different parts and units must be manufactured to fit well into the method of production. Simple interfaces is one key feature to simplify the assembly of the final product from different parts manufactured at different places.
For all types of radio communication devices, the part between the antenna and the active components of the RF front-end is critical for the total performance of the radio communication device. This is because all losses that are introduced here are critical from a system point of view. On the receiver side losses that occur before the Low Noise Amplifier (LNA) degrades the sensitivity of the receiver. On the transmitter side, losses that occur after the Power Amplifier (PA) causes degradation of the transmitted power, forcing the PA to transmit at a higher output level.
For portable terminals with energy provided by battery power, these factors are even more critical. Reduced receiver sensitivity causes the device to perform worse in areas with low signal levels. A higher output level from the PA increases the energy consumption from the battery, thereby reducing the available active operation time.
Modern manufacturing methods for devices, such as portable telephones, is based on modules that are assembled in a final assembly line. This procedure requires simple and reliable interfaces between the modules. This typically implies that the interfaces have large tolerances, making them hard to specify tightly. Specifically, this means that the loss in the interface can be quite large.
In order to obtain improvements in these respects some new principals for designing and assembling the products are necessary. Among them, the method of installing the antenna device and at least some of the required RF components must be improved.
Resistive losses, for instance, can be substantially reduced by shorting the connection lines between the antenna elements and the required active analogue components, such as filters, amplifiers, etc. This can be obtained by mounting the components close to the antenna elements, and preferably on a common support structure in order to form a separate antenna module.
This is of specific interest for future Software Radio, SR, architectures where the function of many traditional RF parts in the terminal are included in the software controlling the signal processor. The number of analogue RF parts, especially analogue filters, are strongly reduced in the software radio architecture. The ideal SR converts the analogue signal to/from digital data as close as possible to the antenna elements. However, some components, such as the Low Noise Amplifier(s), LNA, the filters to reduce strong interfering signals and noise, the Power Amplifier(s), PA, and the duplexers to separate transmitting and receiving signals, must still be made as analogue components. Thus, it would be a great advantage if the radio communication device could be assembled from modules, for instance a complete RF module including all analogue RF parts and the antenna, and a digital module comprising the signal processor, and a simple interface therebetween.
In more detail a number of advantages can be obtained by such a proposed complete RF module. One is the reduction of losses mentioned above. Another is the simpler RF interface enabled by feeding a lower power from the transmitter circuitry in the digital module to the RF power amplifier in the RF modul, and by amplifying the received power before feeding it from the low noise amplifier in the RF module to the receiver circuitry in the digital module. The proposed position of the interface between an antenna module and a radio module means that losses in the interface is not critical. This reduces the requirements on the tolerances of the interface (e.g. the contact pins) so that a more favourable assembly method can be chosen.
A further advantage can be the simplification of the duplexer, triplexer, etc. function if more than one antenna is used, e.g. separate receiving and transmitting antennas. To implement this in an efficient way it is necessary that this function is part of a complete RF module. An additional advantage is obtained by a mechanical integration in order to utilize the volume below the antenna element as well as possible. By using the physical area of the antenna module to mount some components needed for processing of the analogue signals the total space required is reduced. This is because the positions of the components can be chosen so that they have a minimum impact on the antenna performance. It is an advantage if the interaction between different components can be controlled, both for antenna performance and for interference, intermodulation, etc.
Preferably, the antenna structure should conform to the exterior casing of the radio communication device. However, the most of the improvement in volume below the antenna element when going from a flat antenna element to an element adapted to the form of the casing is being obtained already when using an element arranged on a carrier having a single curvature only.
In this disclosure it is to be understood that the antenna device of the invention is operable to transmit and/or receive RF signals. Even if a term is used herein that suggests one specific signal direction it is to be appreciated that such a situation can cover that signal direction and/or its reverse.
A main object of the present invention is to provide an antenna device which is easy to manufacture, easy to mount and which enables an efficient use of the available space, and has good antenna performance.
An other object is to provide an antenna device in which internal losses due to the resistivity in connection lines have been reduced.
A further object of the invention is to provide an antenna device which can be formed as an easily installable antenna module also including processing capacity for analogue RF signals.
An additional object of the invention is to provide an improved antenna device with processing capacity for analogue RF signals which can be formed as a module which via a readily connectable interface can be connected to a signal processor of a software radio module.
A further object of the invention is to provide an antenna device comprising matching circuits so as to let said antenna means be connectable to a connection point having a specific, matched, impedance, for instance 50 ohm.
A still further object of the invention is to provide an antenna device which is designed as a built-in module.
Another object of the invention is to provide an antenna device which can be adapted to the shape of the casing of the radio communication device it is to be installed in.
These and other objects are attained by an antenna device as claimed in claims 1-47.
Claims 31-47 of these claims relate to antenna devices of the kind generally named Planar Inverted F-Antennas, PIFA, modified in accordance with the present invention. The space occupied by such a modified PIFA is more effectively used since circuitry is accommodated inside the antenna. An other advantage of this design of a PIFA is that such circuitry can be placed in the immediate vicinity of the antenna feeding point, thus avoiding transmission losses.
According to a preferred embodiment of the invention an antenna device is provided comprising duplexer, or switch means for combining transmitting and dividing receiving frequencies, filter means for filtering transmitting and receiving frequencies, low-noise amplifier means for amplifying the receiving frequencies and, possibly, power amplifier means for power amplifying the transmission frequencies, as well as a connection device for easy connecting the signal lines to a connection point having a specific impedance, for instance 50 ohm, and further coupling the signals to RF circuitry in the radio communication device.
According to an other embodiment of the invention an antenna device is provided comprising means for securely holding a SIM-card and connecting said SIM-card to circuitry in the radio communication device.
An additional object of the invention is to provide a radio communication device comprising an antenna device manufactured to fulfill the main object of the invention mentioned above. This object is obtained by a radio communication device as claimed in claims 48 and 49, respectively.
An advantage, according to one embodiment of the invention, is that the space occupied by a PIFA is more effectively used since circuitry is accommodated inside the antenna which otherwise would have to be placed in the surrounding areas.
An other advantage, according to one embodiment of the invention, is that circuitry essential for the effective operation of the antenna can be placed in the immediate vicinity of the antenna feeding point, thus avoiding transmission losses. The feeding point being the point inside said cavity connecting said feeding means to said feeding post.
Another advantage, according to one preferred embodiment of the invention, is that it is possible to achieve a matched antenna having connector means with a specific impedance, for instance 50 ohm.
The invention is described in greater detail below with reference to the embodiments illustrated in the appended drawings. However, it should be understood that the detailed description of specific examples, while indicating preferred embodiments of the invention, are given by way of example only, since various changes and modifications within the scope of the claims will become apparent to those skilled in the art reading this detailed description.